It is desirable when designing a lock for a vehicle door to provide a mechanism which will ensure the complete locking engagement of a ratchet with a striker when the door is closed, and which will lessen the possibility of the door becoming unlatched, for example in a collision. It is desirable as well, to design a mechanism which will not be functionally disabled by a collision such that after a collision it is still possible to unlatch the door permitting passengers to leave the vehicle.
It is known that in some instances that during particularly a frontal or side collision the shock of the collision may cause a side door normally in a closed position to buckle and separate from the body of the vehicle in a lateral direction relative to the length of the vehicle. In some instances the extent of such lateral force is sufficient only to urge the engagement surface of a ratchet normally engaging the striker, laterally against the striker. If the ratchet is not secured in a primary engagement position as for example by a detent projecting from a pawl, then such minor lateral forces may be sufficient to pivot the ratchet releasing the striker causing the door to fly open.
In more serious collisions, it is known that force transmitted laterally relative to the length of the car tends to cause the doors to fly open if transferred to the locking engagement of the ratchet with the striker, possibly deforming the ratchet sufficiently to break and thereby release the striker. The resultant unresolved twisting tends to rotate the ratchet in a plane which is not perpendicular to the axis of the striker, thereafter binding such an engagement and preventing normal opening of the door.
In the most common vehicle door latch design wherein the striker comprises a substantially cylindrical shank having a head of extended diameter at the end thereof, the head portion and shank sliding into a horizontally extending slot disposed within the door closed at one end, the ratchet encouraged to rotate by said striker, thereby engaging the shaft behind the head of the striker and thereby preventing the striker from exiting the slot. However, the latch does not rigidly hold the door closed as there is a certain amount of free play resulting in rotating of the door in time. Such rotational forces are usually not in a single plane, and the tendency during a collision is for either the head of the striker to partially or totally shear away from the locking engagement with the ratchet or the ratchet will bend, buckle and twist, thereby disabling the mechanism. Examples of such "pin" type vehicle door locks may be seen in U.S. Pat. Nos. 3,674,296, 4,130,308; 4,357,039; 4,358,141 and 3,367,699.
In an effort to compensate for the rotation of the ratchet relative to the striker in a collision it is known to provide a striker having a structure which is tapered in one axis. Such a "wedge shaped" striker is mounted on a vehicle pillar. The wedge shape is generally horizontal inclined with the smaller cross section of the wedge leading the advance of the striker into a slot for engagement thereat with a ratchet. An example of a wedge shaped striker may be seen in U.S. Pat. Nos. 4,165,112 and 4,219,227 As appears from U.S. Pat. No. 4,219,227 a ratchet engages a depression in the wedge shaped striker. As appears from U.S. Pat. No. 4,165,112 the striker has a hole through it, through which a leg of a U-shaped ratchet passes when the mechanism is engaged. It will be appreciated by those skilled in the art that such an arrangement would tend to prevent rotation of the striker in relation to the housing therefor.
Further it will be appreciated by those skilled in the art that proper engagement of the ratchet with the hole in the striker is very necessary. To this end, such a mechanism requires careful design and installation which ensure in continuous use that when the door is closed, the ratchet will be aligned with the hole in the striker for engagement therewith. Various bumpers, guides and elastomeric devices have been proposed to assist such an alignment. In U.S. Pat. No. 4,219,227 and in an older U.S. Pat. No. 3,858,919 a cone shaped pin is mounted in the slot receiving the door striker. The door striker has a cone shaped recess which slidably fits over the cone shaped pin when the door striker is engaged in the slot for locking. It will be appreciated by those skilled in the art that while the foregoing mechanisms may provide for proper alignment with the aid of bumpers, elastomeric devices and shims during installation. Further such a device may assist in reducing rotation in a plane perpendicular to the axis of the door striker. However the mechanism will still permit longitudinal separation of the striker from the slot in a longitudinal direction in for example the axis of the striker extending away from the pillar generally in the lengthwise direction of the car. Furthermore, because of the design tolerances required it is likely that any deformation of the locking mechanism components concomitant with a collision will cause jamming, resulting in difficulty for a passenger to release the locking mechanism in order to leave the car.
It is known in the art to provide an engagement between a striker and a slot for receiving the striker which will resist the longitudinal separation of the striker from the slot for receiving same. For example, U.S. Pat. Nos. 1,192,733 and 2,100,591 disclose a "hook shaped" striker. The hook or projection of the striker fits into a slot which is generally Ushaped and surrounds the hook, thereby preventing longitudinal separation. In the U.S. Pat. No. 2,100,591, a bolt slides internally of the U-shaped slot for engaging a corresponding aperture in the hook. In this manner, the hook cannot slide out of the recess.
In U.S. Pat. No. 2,758,864 a locking mechanism is disclosed wherein the striker is generally T-shaped in cross section and may be slidingly keyed into a slot having the same T-shaped cross section. The leading edge of the striker having a T-shaped cross section is formed with a cam surface for displacing a spring biased latch bolt which may slidably enter the slot. When the door is closed the cam surface of the striker raises the latch bolt. The latch bolt passes over the striker to the back) of the striker and blocks its exit from the slot. It will be appreciated by those skilled in the art that such an arrangement is similar in principle to the traditional arrangement of a striker pin engaging a pivotable ratchet which once engaged blocks the exit of the striker pin from the slot.
In United Kingdom Patent 239,691 there is provided a latching mechanism for use in a motor vehicle wherein the "striker" slidingly engages a slot in a latch housing. The striker is of a generally T shaped cross-section the head of the striker is tapered in two directions, being wider at the base than the leading edge and has a transverse taper from the base at the back, to the front. The neck of the striker is also tapered, being wider proximate the base than the leading edge. The slot is tapered in two directions comprising a "V" shaped taper matching that of the neck of the striker and a transverse taper matching the transverse taper of the head of the striker. The combination, of the transverse taper of the striker head and the transverse taper of the slot draws the striker and the latch housing together when placed in engagement. It will be appreciated by those skilled in the art that the transverse taper is not symmetrical. Exact alignment of the striker with the slot is therefore required during design and installation thereof.
In U.S. Pat. No. 4,466,645 a U-shaped striker is disclosed having a part covered by a mould-formed plastics material, the portion of which carried at the juncture of one corner of the horizontal connector and leg which is pushed into a door latch being thicker, to present a columnar shape.
It is therefore an object of this invention to provide a resiliently biased vehicle door locking mechanism which will provide for the broader tolerance engagement of a striker in a latch housing therefor.
It is a further object of this invention to provide a vehicle door locking mechanism which will ensure the complete engagement of a ratchet with a striker when the door is normally closed, thereby avoiding the unintentional opening of a door.
It is a further object of this invention to provide a vehicle locking mechanism which will evenly distribute the load in a collision, thereby avoiding the forced opening of a door in a collision, by resolving any forces upon the mounting members of the ratchet mechanism and not upon the ratchet mechanism itself.
It is a further object of this invention to provide a vehicle locking mechanism better adapted to withstand collision, whereby the ability of passengers to unlatch the door after a collision will be facilitated.
It is a further object of this invention to provide improved strikers of simple construction yet effective for use in a locking mechanism.
Further and other objects of this invention will be apparent to those skilled in the art from the following summary of the invention and detailed description thereof.